It took several minutes on a couple of Macs with fusion drives. It seemed stuck at "Calculating time remaining..." but eventually finished, rebooted, and continued installing, this time displaying a reasonable time remaining value.
I had this problem with the last Sierra update. Have not pulled the trigger on High Sierra yet.
Yep, no problems (on a 2012 Air). Doesn’t seem to have fixed the Month 13 problem though…
No problem on Air 2012. Upgrade took shorter time than my shower. :D